Method of heating



Dec. 15, 1936. A DUNHAM ET AL 2,064,197

` Y METHOD oF HEATING Filed Jan. 8, 1932 6 Sheets-Sheet 1 Dec.15, 1936. c. A. DUNHAM ET AL METHOD OF HEATING Filed Jan. 8, 1952 :W 101 f 3.7 i o 102 w 6 Sheets-Sheet 2 Jet m7151936. QADUNHAMHAL 2,064,197

METHOD oF HEATING Filed Jan. 8, 1932 e sheets-sheets orgs.

Dc 15, 1936 c. A. DUNHAM Er AL 2,064,197

. -METHOD OF HEATING Filed Jan. 8, 1932 6 sheets-sheet 4 Dec. 15, 1936.

C. A. DUNHAM El' AL 4METHOD oF HEATING 'Filed Jan. s, 1932 Dec, l5, 1936. c. A. DUNHAMET 11u.` ".72'064197 METHOD QF HEATING l Filed Jan. 8, 1932 6 ShetS-She'et IVN" v Patented Dec. 15,'

METHOD oF HEATING Clayton Arunham; Glencoe, Ill.,` and David N. Crosthwait, Jr., Marshalltown, Iowa, assignors to C. A. Dunham Company, Iowa, acorporation of Iowa Marshalltown,

Application January s, 1932, semi No. 587,342'

z claims. (cuasi-12) This invention relates to new and useful improvements in effective temperature heating systems, and more particularly to improved meansfor automatically controlling a heating system sov that the heat output will maintain a substantially constant condition of human comfort Within 'the building being heated'. i

It is a matter of common experience that at times, even though a building is maintained at a fixed* temperature, this temperature produces sensations of discomfort. For example a temperature of 70 Fahrenheit may, at times, cause a person to experience a sensation of being chilly.

At other times, a temperature of 70 Fahrenheit may produce a sensation of being too warm. It is usual to encounter the rst experience when the humidity is low, Iand the latter when the humidityA is high, that is, when the moisture content of the air within the building is greater. Human comfort depends upon the heat dissipation by the skin surface. kwhen the humidity nf creases, the heatA abstraction ,fromv the skin for a given air movement and temperature decreases, and the sensation of being too warm results. When the humidity decreases, therate lof heat abstraction from the skin for the same air movement and temperature increases, withthe result of producing'a-chilly sensation.

In previous efforts to produce a condition of 30 constant comfort, the practice has been to conrol the humidity, as Well as the temperature. To do this requires humidifying apparatus in addition to heating apparatus, which is commerf cially impractica-ble for many typesof structures liavingfvarious types of occupancy:

According to the method proposed herein, as

one feature of this invention, constant comfort is provided by varying the temperature of the inside air with variations in humidity by increasf 40 ing the rate of heat supply automatically as the humidity decreases, and vice versa. It has been determined experimentally that there exist certain combinations of temperatures andhumidities for a given air motion which produce the same feeling of comfort or discomfort. These combinations of -temperatures and humidities which produce equal conditions of comfort have been charted, and the lines passing through these equally effective air conditions are known as equal comfort lines, and the term effective temperature? as used herein is used to indicate the constart temperature sensation, although the actual dry bulb vtemperature which produces this sensation will vary as the humidity varies. A maximum number of people will feel comfortable at an effective temperature of 64 Fahrenheit, and this is called the comfort line. While at rest in still air, 97 percent of all people are comfortable at this temperature. f A

In maintaining' effective temperatures, it is essential .not to produce chilly sensations, as' a result of the absence of radiant heat. This means that heat must -be supplied to a building at substantially the same rate the building is losing it, that is so long as heat supply is necessary, this 1. heat should be supplied continually and not intermittently. Also, to maintain the most desirable comfort conditions, the temperature of the air in different parts of the rooms or at various elevations must be substantially uniform. The-1; temperatures at the Vheights of the knee and at the oor and ceiling. should approach the temperature at the breathing line as closely as possible. The foregoing is another way of saying that there must `be minimum stratification of the air within the room or rooms-withl regard to temperature conditions. 'Ihis latter condition is best maintained` when the heating medium which 'supplies heat to the room does not impart excessive temperatures to the airpassing over it in 25 response to convection currents, and this requirement is best met when the appliance delivering the heat, maintains temperatures whichapproach, as closely as is possible, the temperature to be maintained.A Excessive heating of the air 30 passing over a steam radiator, for example, causes the temperature at theceiling to be higher than is the case where the air passing over the radiator is not so highly heated. This condition is best maintained by utilizing steam at con- 35 trolled sub-atmospheric pressures as the heating --medium, as broadly disclosed in the patent to -Clayton A. Dunham, No. 1,644,114, granted Oct.

4, 1927, and in the copending application of David N. Crosthwait, Jr., 4Serial No. 425,681, led 40 Feb. 3, 1930. The presentinvention relates to a modicationof, and improvement'on, the heating systems therein disclosed.

Obviously, the/ most 1 satisfactory result in maintaining equal comfort conditions such as 45 above described are only'obtainable when the system is completely automatically controlled. According to the present invention, the supply of steam to the'radiators is primarily controlled automatically` in response to variations in the 50 pressure differential -between .the supply and discharge sides of the radiators so as to constantly maintain the radiators lled or partially filled with steam at a temperature just sufcient to replace the heat loss from the building. In y addition, thermostatic control mechanism is provided for cooperation with the pressure-control mechanism to insure the restricting of temperature variations within the building within certain predetermined limits.

Inaddition, humidity responsive mechanism cooperates with the thermostatic control mechanism so as to vary the actual temperature maintained in accordance with variations in humidity so that a substantially constant predetermined effective temperature will be maintained within the building, thus producing approximately constant comfort conditions'. In addition, this inventionincludes various improvements in details of the control mechanism and combinations thereof, whereby these equal comfort conditions are automatically and constantly maintained, or varied at different times in the day as circumstances may require or make desirable. j

The general object of this invention is to provide an improved heating system for maintaining constant 'comfort conditions within a building, as briey described'hereinabove and disclosed more lin detail in the specifications which follow.

Another object is to provide an improved method of proportioning the rate of heat supply to a building so as to maintain constant effective temperatures. v

Another object is to provide a new method for automatically maintaining temperatures within a building which yield equal comfort conditions to human occupants.

Another object is t provide an improved au-v tomatic control of all the auxiliaries of a steam heating system in proper sequence so as to supply-steam continually and at as'low a temperature as is possible to maintain the desired effective temperature.

Other objects and advantages of this inven tion will be more apparent from the following detailed description of certain approved forms of apparatus designed and constructed according vto the principles of this invention and cooperating to produce the desired results as hereinabove and hereinafter disclosed.

In kthe accompanying drawings:

Fig. 1 is a diagrammatic elevation of a subatmospheric steam heating system with the improved control mechanism applied thereto.

Fig. 2 is a central vertical section through the improved steam-control valve.

Fig. 3 is a partial side elevation of the control valve, looking from the right at the lower portion of the mechanism shown in Fig. 2.

Fig. 4 is av comfort chart illustrating the combinations of dry bulb temperatures and percentages of /humidity which correspond to the effective temperatures.

Fig. 5 is a front elevation of one of the improved thermostats.

Fig. 6 is a front elevation of the thermostat with the cover removed, Athe thermostatic element being shown in vertical section.

Fig. 'Tis a side elevation looking from the right at the apparatus shown in Fig; 6.

Fig. 8 is a vertical section, taken substantially on the line 8--8'of Fig. '1.

Fig. 9 is a front elevation of the control panel.

Fig. l0 is a wiring diagram of the .control panel, the thermostats, the motor mechanism for operating the valve, and the pump controlling mechanism. l

Reference will first be made to Fig. 1 which shows a heating system of the type with' which this improved control mechanism is best adapted- 425,681-, hereinabove referred to. This heating system comprises a boiler or generator A from which the steam flows through supply main B and the improved flow control valve C into the portion B" of the steam main, from which the radiators -D are supplied. At the outlets of the radiators are steam traps E, Fis the return main, G is an accumulator tank for the condensate, vtheeirhausting mechanism is indicated generally at H, and J indicates the differential pressure controller for the exhausting mechanism. At K is indicated generally an electric controlling mechanism for the valve C, at L and L are indicated the improved thermostatic control devices, and M is the improved control panel through which all.of the manual and automaticl control operations are coordinated, and on which the condition of the different elements of the heating system is indicated.

The reduced pressure steam in main B' passes through risers I and inlet valves 2 into the respective radiators D. Suitable orice plates, such as disclosed in the Dunham patent hereinabove referred to, may be interposed in the respective risers I, preferably between the inlet valves 2 and the radiators for proportioning the steam flows. to the respective' radiators in accordance with the size or condensing capacity and location thereof. The steam traps E are adapted to close lwhen the radiators are lledwith steam'and4 `prevent the escape of steam therefrom. When condensate and non-condensable gases accumulate inthe radiators, the traps E will open and permit the condensate and non-condensable gases to flow out or to be drawn out by the lower pressure maintained in the return side of the heating system. These gases and the condensate flow through pipes 3 into return main F and thence through the strainer 4 into the accumulator tank G. densate and gases accumulating in the portion B of the supply main pass out through float andl thermostatic trap 5 into return main F and thence into the accumulator tank. The exhaustingmechanism H comprises a separator tank 6 and a pump "I, driven by motor 8 to withdraw water from the lower portion of tank 6 and force In a similar manner,A the con- A it through ejector 9 and thence back into the upper part of tank 6, together with the gases and condensate which are withdrawn from accumulator tank G through pipe I0 and checkvalve II into the exhauster casing. The gases 'are vented from separating tank 6 through pipe I2 provided with outwardly opening che'ck valve I3. When a certain amount of liquid has accumulated in vtank 6, a float-controlled mechanism, indicated ygenerally at I4, operates to open a normally closed valve I5 so' that the pump I can force a part of the liquid out through pipe I6 provided with check valve I1, and thence -through pipes I8 and I9 into the boiler.

necessary to transfer accumulated condensate from the accumulator tank G into the separating 75 A open to equalize the pressures.

the upperportion ofthe casing 32.

tank 6. The control mechanism J comprises a.

` diierential-pressure controller 20 which automatically opens and closes a switch 2| which operates through starter 22 to control the motor 8. The diierential pressure controller comprises supplyand return sides of the heating system,

fthe ,relatively low pressure surge chamber 25.

This valve opens toward the high pressure. side of the system and will normally remain closed ,unless for somel reason a lower pressure tem.

porarily exists in the supply main than the pressure in the return main, whereupon valve 38 will This control mechanism J will operate, in a well known manner, to cause the exhausting mechanism' to function whenever the pressure diierential between lthe supply and discharge sides of the heating system falls below a predetermined minimum, and to throw the exhausting mechanism out of operation whenever the desired pressure differential has again been established. Also, a floatcontrolled mechanism in the accumulator tank G (disclosed in detail in the Dunham patent rei ing an internal web 33 separating the high pressure chamber 34 from the relatively low pressure cooperate respectively the connected and substantially balanced valves 38 and 39. VEach'of -the valves 38 and 39 is preferably of the sleeve type here shown, with the slots or vopenings. 39 in the sleeve walls so designed that the total area fof the valve opening will increase by equal increments as the valve is moved upwardly. A removable closure plate 48 permits access to A closure plate 4| covers the opening in the lower portion of casing 32, this closure plate having an outwardly projecting ange 42 securedto the casing by bolts 43, and an upwardly projecting ange 44 to centerthe plate 4| properly within the opening in the lower portion of the casing; 'Ihis closure plate 4| is formed integrally with an upward extension 45 of the diaphragm casflange 49. The two casing members 46 and 48 i are clamped together -at opposite sides of an. enclosed exible diaphragm 58 by means of a `plurality of bolts V|l passing throughthe anges 41 and 48 and the peripheral portion of daphragmA 58. The chamber 5| within the lower casing member 48 `is open to the atmosphere through central passage 52. The chamber 53 above the. diaphragm 58 is connected through intermediate chamber 54 with an upper chamber 55 from which leads a pipe 56 which extends to a surge chamber 51 communicating through pipe 58 with the supply main B. The chambers 53, 54 and 55 are all`at substantially the same pressure, but the intermediate Webs or baiiles 59 are -designed to. preventcthe formation of convection currents in the liquid that accumulates above the diaphragm 4and thus prevent undue heating of the diaphragm 50 from `the steam passing throughfcasing 32. The upper portion 68 of the lower diaphragm casing is supported from the lower vportion 48 of the upper diaphragm casing by means-of a plurality of struts 6|. The lower member -62 of this lower diaphragm casing is clamped to the casing member. 60 by means of a plurality of bolts 63 so as to enclose a second exible diaphragm 64 similar to the rst describeddiaphragm 50. The vchamber 'V 65 above diaphragm 64 is open to the atmosphere through central passage 66. The lower diaphrag'm chamber 61 is connected through pipe 68 with` a surge chamber 69 which in turn is connected'through pipe 10 with return main F. 'Ihe surge chambers -51 and 59 may be conveniently positioned adjacent one another and connected by the supporting member 1|,y although thereis no uid' connection between these two chambers.

The upper end of a valve stem 12 is threaded in valve structure 13 and provided with a lock nut 14. The valve stem 12 is slidable through a Aguide bearing 15 in the closure plate 4| and also passes vertically downward through central passages in the webs 59. The lower threaded portion 16 of stem 12 passes through diaphragm 58 Aand is sealed thereto`by means of the diaphragmvplates 11 and'18 held -in place by nuts 19 and 80. The outer edges of the diaphragm plates are preferably curved, as indicated at 8|, to prevent any cutting action on the diaphragm as it is exed. The lower end of the stem 12 is screwed into the yoke 82 and locked in kplace by nut 83. A lower valve stem 84 is similarly threaded into the lower side of yoke8'2` and locked in place by nut 85. `This valve stem 84 -is sealed into the lower diaphragm 64 bymeans of diaphragm plates 86 and 81 held in place by nuts 88 and 89, in the/same manner vas the uppervalve stem is attached to the upper diaphragm. y s E A lever 98 is intermediately pivoted at 9| to the lower end of a fulcrum link 92 suspended from lug 9,3 on the lower diaphragm casing member 48. One end of-1ever 90 is pivoted at v94 within the yoke 82. The other arm of lever 9|) carries a weight 95 suspended by stem 96 and yoke 91 which is adapted to rest in any one Aof 'a plurality ofvnotches 98 spaced lengthwise of the longer arm of lever 90. It will be apparentl that by adjusting the weight 95 outwardly on the-lever arm 90, the upward pressure exertedv on the movable valve assembly will be increased.

A stop-screw 40 mounted in the bottom of closure plate 48 limits the upward movement of valve assembly 13.-

`Itvwill be noted that opposed sides ofthe two connected diaphragms 50`and 64 are `'exposed 75 to atmospheric pressure, but the upper side of the upper diaphragm 59 is subject to the pressure in thel supply side of the heating system, whereas the lower side of lower diaphragm 64 is subject to the pressure in the return side of the heating system. Therefore, the net force tending to move the valve assembly downwardly to close the valve is always equal to the pressure differential between the supply and return sides of the system. It will now be apparent that when this downward force exerted by the pressure differential just equals the upward force exerted by the adjustable weight 95, the valvesv will be in a state of rest or equilibrium. If the pressure differential increases above this xed normal, there will be a tendency to overcome the effect of weight 95 and close the valves. On the other hand, if the pressure differential decreases,

the `weight 95 will overcome the uid pressure and open the valves.

In case the valves 38 and 39 are absolutely balanced, that is of equal size, the device will operate as above described. In case a semibalanced valve assembly is used, the varying pressure effect may be compensated for by employing larger diaphragm plates on one of the diaphragms than the diaphragm plates used on the other diaphragm. lThis will change the effective area of the flexible diaphragms and compensate for the unbalanced areas of the two valves. The unbalanced pressure due to the difference in elevation between the two dia- `phragms 59 and 64 may be compensated for by a` proper variation in the relative sizes of diaphragm plates TI, 'I8 and 86, 81.

In the general operation` of the heating system as thus far described, the desired steam pressure in the boiler A and supply pipe B is obtained by proper control of the -res beneath the boiler A, or by the dampers or other heat controlling mechanism with which the generator is supplied.` The weight 95 is set to respond to a predetermined pressure differential between the supply and return sides of the system, and the differential controller J will be regulated to maintain substantially the same or a somewhat smaller pressure differential. Assuming that the temperature in the building is below that at which the thermostat L .(or L as hereinafter described) operates to close the valve C, and that the system is not yet lled with steam, the weight 95 will operate to open the valves 38 and 39 and permit a free flow of steam through' the valve C. The exhausting mechanism H will now be in operation to lower the pressure in the return main, and this exhausting action will extend throughout the system since the traps E are now open. The traps will remain open until 'the radiators D are filled with steam, and during this time the exhausting mechanism will be unable to establish any material pressure .differential between the supply and Areturn mains. When the steam lls the radiators D and reaches the traps E, the traps will automatically close, after which the exhausting mechanism H will be able to establish a lower pressure in the return main F than exists in ,the'supply main B'. As this pressure differential reaches the predetermined value, it will act on the diaphragms 50 and 64 to overcome the effect of weight 95 and tend to close the valves 38 and 39, thus throttling the flow of steam to the radiators. As the operation of the valve is gradual, the valve in closing will reach a position where the rate of steam supplied to the radiators is approximately equal to the rate of steam consumption or condensation in the radiators, so that the differential will remain substantially constant and the valve will ytend to remain in a state of rest or equilibrium in that position for feeding steam to the system at the rate at which it is required. If, for any reason, the rate of steam supply should exceed the desired rate of heat emission from the 'radiators, or that rate at which the radiators will condense steam to compensate for the heat lost from the building, the pressure diierential will increase and the valve C will tend to close. The condensing rate of the radiators will then exceed the rate at which steam is being supplied and the supply pressure will drop so. that the differential will diminish and the valve C will tend to open again under the influence of weight 95. It will be apparent that any increase in pressure differential will tend to cause the valve to close and any decrease in the differential will tend to cause it to open, and that the gradual action of the valve in opening and closing between its extreme limits of travel will permit it to reach a position of substantial equilbrium that maintains the steam supply substantially equal to the condensing rate.

It will now be apparent 4that in view of the fact that the valve C will act to maintain the proper differential at all times and that this can only be accomplished when steam is lling the system at the rate that the system is condensing it, the valve C will act to maintain varying steam pressures in the radiating system in accordance with outside temperatures. This will result in the heat emission from the radiators remaining substantially equal to the heat loss from the building.

It is to be noted that in the construction of the improved control valve C no stuffing boxes are required. One side of each of the movable diaphragms 59 and 64 is exposed to the atmosphere, whereas the pressure chambers at the other sides of the respective diaphragms will become lled with liquid so as to prevent the direct contact of steam with the diaphragms, thus effectively sealing the System against the loss of fluid pressure and prolonging the life of the diaphragms by protecting them from the direct action of the gases in the system.

The construction and operation thus far` described is substantially the same as that disclosed and claimed in the copending application of Crosthwait, Serial No. 425,681, hereinabove referred to.

In addition to the pressure-operated controlling mechanism hereinabove described, thermostatic means is provided for automatically closing the valve or limiting-its' closing 'movement in accordance with variations from a predeterminedtemperature to be maintained throughout the building that is being heated. Furthermore, humidity-responsive means is combined with the thermostat so as to vary the standard temperature maintained by the thermostat and its cooperating control mechanism in accordance with variations in the relative humidity of the air within the building so as to maintan a sub! stantally constant effective temperature, that is a constant comfort condition.

The valve C is under the direct control of a motor mechanism indicated generally at K,

mostatic mechanisml L. Referring again to Figs. 1, 2, and 3, an operating lever 99 is intermedi- 4ately pivoted at |00 between brackets |0| projecting downwardly from the upper diaphragm casing 48. -The inner end |02 of lever 99 is adapted to engage a portion of yoke 82 so that 'downward movement of this inner arm .of lever 99 will positively pull valve stem 12 downwardly to close the valves 33 and 39. However, the inner arm of lever 99 can-swing upwardly independentlyjof the yoke 82. In this manner the lever 99 is operable to close the valves or to limit the amount oftheir opening movements, but the actual opening movement of the valve is `under the control of the pressure-operated mechanism previously described. A yoke -|03 formed at the outer end of lever 99 is pivoted at |04 to a slide block |05 mounted on the operating stem |06. surrounds the stem4 |06 and is confined between block |05 and an adjustable nut |08. At |09 is a stop nut adjustably mounted on the upper end of the stem |06 to limit the upward movement of block |05. At is indicated a small motor assembly which is supported'bya bracket projecting from the lower portion of the valve assembly. A rotary operating shaft ||2 projects from the motor casing ||0 and carries at its outer end a crank arm ||3, towhich the lower end of operating stem |06 is pivotally connected at H4. Operating means (hereinafter described) are provided within the casing H0, whereby crank arm ||3 will be rotated intermittently, in one direction or the other, an amount proportionate to the variation from a .certain predetermined effective temperature as registered by the thermostatic mechanisms L po- 'sitioned at suitable locations within the building.

' This movement will be transmitted` through stem |06 andI springs|01 to the operating lever 99, which will impart a corresponding. closing movement'tothe valves 38 and 39, or will so ward the right.

v right of the chart are the effective temperature perature readings are indicated on the scale along the top of the chart, and by the approximately horizontal lines sloping downwardly to- The percentages of relative humidity in .the air -are indicated by the lines curving upwardly from the left hand side of the chart. The lines sloping downwardly at approximately 45 from the upper left to the lower lines. that is lines indicating temperature and humidity combinations which will produce sensations of constant comfort to the occupants of the building. The shaded area is known as the comfort zone (any effective temperatures within this zone -being considered comfortable by the average human being) and the heavy line passing through the point corresponding to dry bulb and wet bulb readings of 64 and 100% humidity is known as the comfort line, the combinations of dry bulb temperatures and humidities corresponding to points on this line producing ideal comfort conditions for the majority of.

relative humidity,

A compression spring |0| y people. For example, with entirely saturated aina dry bulb temperature of 64 will establish an approximately ideal condition of comfort within the building. If'the air hasta 50% relative humidity, the ordinary dry bulb temperature should be approximately 69, For a 10% the ordinary temperature reading would be. 76, etc. It will thus be seen that in order to maintain a desired eifective,

temperature' of, for example, 64, it is necessary to vary the ordinary or dry bulb temperaturel of the air within the building in accordance with` changes in the relative humidity of the air. In other words, the thermostatic mechanism hereinafter 'described does not maintain an absolutely standard dry bulb temperature, but varies this standard temperature in accordance with changes lin the relative humidity of the air,v so as to maintain .a constant standard eective temperature which will maintainconstant conditions of comfort.

Referring nowmore particularly to Figs. 5, 6, 7, and 8, the instrument here disclosed by way of example for maintaining the desired standard ,effective temperature-by responding simultaneously to variations in the' dry bulb temperature and also to variations in the humidity of the air, will be described in detail. The operating `elements of this instrument are mounted on a supporting base ||5, and enclosed by a removable casing or coverl ||6 provided with openings ||l for the free passage of air therethrough. On cover I6 ismounted an ordinary dry bulb thermometer ||8, at the right of which is a scale |9 indicating the eiective temperature, and at the left, a scale |20 indicating the corresponding relative humidity. This thermometer is merely for the no part of the automatic controlling mechanism.

Referring now to Figs. 6, 7, and 8, a suitable electric resistance element |2|, preferably in the form of an exposed resistance coil, is connected at one end by wire |22 with a binding post |23, and is connected at the other end by a wire |24 with a. binding post |25. A contact member |26 is in constant engagement with the resistance element |2| intermediate the 'ends thereof,

and is movable to adjust its position on the resistance by mechanism hereinafter described.

This movablecontact |26.is connected by wire |2l.with a binding post |28. The three control wires |29, |30 and |3| (see Fig. 10) extend respectively from the binding posts |28,l |23 and |25. It will be noted that the resistance |2| is divided? into two effective resistances |2| and |2I", the relative values of which will change,

`dependent upon the position lof movable contact |26 intermediate the ends of resistance |2|.

- One of these resistances |2| is positioned between two of the circuit wires, such as |29 and |30, and the other resistance |2|" is positioned between the other two circuit wires |29 and |3i. The variations in the krelative currents passing through these two circuits (depending upon the relative values of the resistance sections |2|' and |2|") operate through mechanismhereinafter described to cause proportionate movements ofthe valve-controlling lever 99 in one directionor the other.

'I'he thermostatic element is'here shown in the form of a hermetically sealed casing |32 containing aquantity of temperature responsive fluid |33, one wall of the casing being in the form of a flexible diaphragm or bellows |34.

-beneflt of the observer at this location and forms The volume of the iluid |33 will change in accordance with changes in temperature, and the flexible bellows |34 will expand or contract in order to adjust the capacity of vessel |32 to the volume of the heat responsive fluid |33. An operating stem |35 extends from the movable end of bellows |34 and is formed with a collar |36 engaging one end of a compression spring |31 which abuts at its other end against a collar |38 carried by an adjustable screw |39. The spring |31 opposesv the movement of the plunger stem |35, and by adjusting the position of screw |39, the amount the thermostat will move for a given temperature change can be varied. A lever |40 is formed with a yoke |4| which straddles the plunger |35, the arms of the yoke being slotted at |42 to receive the ends of a pin |43 secured in the plunger. The lower vend of lever |40 is fulcrumed at |44 on an adjusting screw |45. The contact member |26 is carried on an insulating block |40 at the upper end of lever |40 by means of the bowed spring |46 which holds the contact yieldably in engagement with resistance |2|. It will be -apparent that the thermostat |32, through plunger |35 swings lever |40 about its fulcrum |44 and thus moves contact |26 longitudinally of resistance |2|. By adjusting the fulcrum screw |45, the relative lengths of the upper and lower arms of lever |40 can be changed, thereby adjusting the rate of movement of contact |26 longitudinally of resistance |2| in response to any given temperature responsive movement at the thermostat.

'Ihe humidity responsive mechanism comprises a long hygroscopic strip or membrane |41 which is anchored at one end |48 to a lever |49 fulcrumed at its opposite end |150 on the base ||5, and intermediately pivoted at |5| to an adjusting screw |52 extending upwardly vthrough an adjusting nut |53 mounted at the top of the casing. The other end of the hygroscopic strip |41 is secured at |54 to the bell-crank |55 fulcrumed at |56. The strip or membrane |41 is so formed that itwill vary its elongation with changes in the relative humidity of the air, the strip elongating with increasing humidity and contracting as the humidity decreases. In order to utilize a membrane of sucient length to give a relatively large operatingmovement, the membrane or strip is passed around a plurality of direction pulleys |51. The spring chored at one end |53 and attached at its other end to one arm |60 of the bell-crank, serves to keep the ilexible strip |41 under tension, so that any changes in the length thereof will cause swinging movement of bell-crank |55 about the fulcrum |56. The operative effect of the hygroscopic strip |41 maybe varied by turning the adjusting nut |53.

The resistance element |2|- is adjustably mounted on a longitudinally movable rack bar |6| by means of screws |62 adjustable in slots |63 in the rack bar. A gear sector |64 meshes with rack bar |6| and is pivotally mounted -on the base member at |65. The upwardly extending arm |66 of bell-'crank |55 is formed with a cam slot |61 in which engages a pin `|68 projecting forwardly from the gear sector |64. y It will now be apparent that the contact member |26 is moved longitudinally'of. resistance |2| a distance which is proportional to dry bulb temperaturechanges to which the`thermostatic element |32 responds. At the same time, the resistance element |2| is moved bodily,.in the direction of its own length, in response to changesin the relative humidity of the air. Assuming, for example, that the air within the building is at a temperature (dry bulb temperature) of 68, and the relative humidity of' the air is 60%. It will benoted from the comfort chart that this corresponds approximately to a point on the comfort line, that is corresponding to an elective temperature of` 64, and if 4the mechanism is in proper adjustment the contact |26 should be positioned substantially equidistant between the two ends of resistance |2|, as shown in the drawings. Assuming now that the temperature of th'e air should be raised to '72 and that the relative humidity remains constant at 60%, .an eifective temperature of approximately 67 will prevail and it will be desirable to reduce the rate at which heat is .imparted to the yair by the heating system so as to lower the temperature to the desired temperature of 68. Under these circumstances, the resistance |2| does not move, but the Contact |26 moves toward the right hand end of the resistance, so as to increase the resistance |2| and decrease the resistance |2| in proportion to this variation in temperature from the desired effective temperature, and this variation in the values-ofthe resistances |2 and |2| will operate, in the manner hereinafter described, to effect a corresponding and proportionate adjustment of the heating system; Let us now assume that at the same time the temperature increases from 68 to 72, there has been a drop in the relative hiunidity of the air from 60% to 30%. It will be noted that a temperature of 72` and a relative humidity of 30% correspond approximately to another point on the 64 effective temperature comfort line, so that under these conditions there is no reason why there should be any change in the adjustment of the heating system. The parts are so adjusted that this decrease in the relative humidity will cause a contraction of membrane |41 suf- 'cient to swing the lever |66 and through cam` `slot |61 and pin |68 oscillate the gear sector |64 and through rack |6| cause a longitudinal A movement -of resistance |2| to the left just sufficient to compensate'for the movement of con-- tact member |26 so that theresistance and contact will maintain approximately the same relative positions now shown. If the relative humidity had only dropped to 50%, it will be noted from the comfort chart that the corresponding effective temperature (with a dry bulb temperature of 2) is approximately 66. The desirability of a decrease in the heat 4output from the' heating system is thus indicated, al

-sistance sections |2| and |2| to eiect a proper proportionate adjustment oflthe heating system. Obviously, if the relative humidity'should rise at the same time that the temperature rises, the resistance |2| and contact |26 will be moved ate change of resistances |2|' and |2|". It will be noted from a study of the comfort chart in opposite directions so as to produce a correspondingly greater increase in the proportionthat the increments of temperature change are not uniform for equal' increments of humidity change. That is, as the humidity decreases,` the dry bulb temperature-,must increase ata more rapid rate, and vice versa. Accordingly, the cam |61 has been provided,'which isvso proportionedx that the movements of the resistancevelement |2| will be in proper relation to the movements of the contactmember |26 to maintain the desired effective temperature.

In the installation here shown by way of i example, two separate thermostats L and L are to changes intemperature only.V Infact,l both.`

of these thermostats, or the single thermostat,` if only one is used, may omit the hygroscopic control feature as far as certain'phases of thisv invention are, concerned, as covered by certain of the claims which follow hereinafter. By employing two separate thermostats L and L',

' the .time controlled element may be mounted other hand, a single time controlled thermostat I. members |26, and the's'eve'ral thermostats will be` connected in series,.all as disclosed and` solenoid coil |16 will lbe changed accordingly.

on the control panel M, thereby' avoiding the. necessity -of incorporating the clock control mechanism in the thermostat itself. On the could be used if desired.'

It is sometimes desirable'to employ a plurality of thermostats positioned in a plurality of locations throughout the building, and so connected with one another and with the valve controlling mechanismthat the heating system will be regulated in'response tothe average eiective tem-y perature registered by all of thesethermostatic mechanisms. mechanism should be modified to embody a pair of separate resistances |2| and engaging contact claimed in the copending application Vof Elbert A. Taymr, et a1., serial No. 585.530, med Jam.

` Referring nowA to the at M atthe right of the figure is the mechanism mounted 'inithe control panel. At the left of the.

gure, in the enclosure indicated at K is shown the proportioning' motor mechanismv and cooperating parts= which`may be mounted in or adjacent the casingk ||8 'carried by the valve C.

-At N is indicated the wiring forthe pumpcontrol mechanism which may, if desired, be

'located adjacent the motor 8 and starter 22,.

In'the panel board .M 'is mounted a doublethrow'triple contact automatic switch O .which is normally thrown to the right when day'therof switch O. The corresponding circuit wires' |29', |38' and |3|' leading from thermostat L' extend to the corresponding set of xed contact members at the left o f switch Q. At P is indicated a double-throw, triple contact, manually operated switch whereby the-heating system may be thrown alternatively from automatic control In such case, each thermostatio wiring diagram shown Fig. 10, enclosed inthe broken lines indicated (by means; of the thermostats) to manual control, -by means of mechanism hereinafter de scribed. When switch Pfis thrown to its upper position, the heating system will be under the automatic control, the three xed upper contact members of this switch beinglconnected by wires.

|18, |1| and i|12 with the threemovable contact members of automatic switch O. From .the three movable contact members of switch `P extend wires |13, |14 and |15, whichlead to they motor mechanism K, wire |14 connecting with the central portion of a solenoid coil |16, and the two wires |13 and |15 extending respectively to,

the two ends of this coil. At |11 is indicated a suitable source of electric Apower from which leads .|18 and |19 extend to the main line switch |88 positioned` on the panel board. From switch |88, wires |8| and |82 lead to the panel-light switch |83, from which wires |84and |85 lead to the panel lights |86 and.- |81 Aby .means of which; .the mechanism mounted on the panel is illuminated'. From the power lines.- |8| and |82, wires` |88 and |89 lead to the primary |98 of a transformer Q. The secondary |9| of transformer Q supplies reduced voltage current through wires |92 and |93 whichare joined to wires |13 and. |15, respectivelyof the' thermo-` static cpntrol circuit.' n y l Assuming now that the power is on, (switch |88 closed), that automatic switch -O is thrown to the Vright and manual switch P isthrown-to its upper position, whereby thermostat L is in automatic control of the system, a low voltage controlcircuit is completed from secondary |9| of the transformerQ., this circuit including two parallel branches, one ofwhich branches includes y portion |2| of the resistance |2| (in the' thermostat L), and also includes one-half, of the solenod coil |16, and th'e other branch including the -When the stronger current is flowing .through the lefthand end'of` coil |16, the core |94 of this solenoid will be drawn to the left, and cori. versely when this end of the coil is the weaker, the core will be drawn to the right. The amplitude of these movements of the solenoidcore'will Y be proportional to the variation in the strengths of these two currents owing through ther'two halvesof the solenoid coil. As lhas been'brought` out. hereinabove, these variations will also be proportional to the-variations in o ne direction' or the other from the standard effective temperature for which thermostat L is adjusted.

At |91 and |98 are indicated the fields of two smallelectric, motors, whose armatures |95 and wheel 28| which is mounted 'on or geared to the in one direction andthe other motor |96 rotates in 'the oppositedirection. The actuating circuit for the motors. and |98 include' a. pair of limit switches 282 and 283, hereinafter described,

and a reversing switch or balanced relay R mounted in the panel board. The reversing switch 13. comprises a pair of 4movable contact members 284, 285 which are moved by the stem 286 -connected with the core 2 81 of solenoid 288.

n |96, respectively, are mounted on shaft |99- car-4 -rying the worm 288 which drives the worm 2| 0, respectively. 'energized the contacts 204 and 205 will assume When the core is moved in one direction, the The engagement of contacts 220 and 22|,of

movable contact members will engage a pair of xed contacts 209 and 2|0 and when moved in the 'opposite direction the movable contacts 204` and 205 will' engage the fixed contacts 2| l and When solenoid 208 is dea neutralr position out of engagement with any of the contacts 209, 2|0 and 2| I. The actuating .circuit for motor |95 extends from power lead |18 through main switch |00, 'wire 2|2, motor iield |91, limit switch 2,02, wire 2|4 to xed con-A tact 2|0 of reversing switch R, movable contact 204, and Wires 2|5, |8| and |19'back to the source of power. In a similarimanner, the actuating circuit for motor |96 extendsA through wire i 2|2, eld |98, wire 2|6, limit switch 203,'wire 2|3 to xed contact 2| of reversing switch R', thence through movable contact 204 back to the source of power as before.

At S (in' the motor `mechanism K) is a proportional control switchactuated from the ballat anced solenoid |16. An actuating stem 2|8' connects the movable core |94- ofsolenoid |16 with able .block-228 from which a pin 229 projects into slot 226. The block 228 is adjustable radially of disc 221 by means of screw 230; 'Y It will now be apparent that when eccentric disc 221 is rotated inl one direction or the other, the switch assembly S will be swung through a small arcin a corresponding direction about the'pivotal axis 224. The amplitude of this swinging movement will depend uponthe eccentricity of pin A229 on disc 221, this being adjustable by means of screw 230. The movable contact 220 ofY switch S is connected through wire 23| with the central contact of solenoid coil 208 on' the panel board. Relatively fixedcontact 22| of switchS is connected 'through wire 23|', wire |13 and wire 232 with the righthand endof solenoid coil. 208.

Fixed contact 222 of switch' S is connected through wire 233wire |15, andwire 234 with the left hand end of solenoid coil 208.

Assuming `now for the moment that theV effective temperature at the location of thermostat L' risesabove the predetermined eiective temperature for which Ithe mechanism is adjusted, this thermostatic mechanism ywill operate so as to move the contact member |26 to the right with relation to resistance |2|, a distance which is proportionate tothe variation from'thev predetermined eec'tive temperature. 'Ihe relative f strength-of the resistance section `|2|' will become greatertthan that of resistance section |2|."., and as a consequence, the strength of the current flowing in the right hand`ha1f or solenoid coil |16 willbe 'proportionately greater than that owing in the left hand half and the core;

|94 will be moved to the right so as to Iswing movable contact 220 into engagement with /xed contact 22|. The distance through which contact 220 is moved to the right (or through which it is attempted to be moved) will -be proportionate to the variation from temperature.

the standard' effective switch S Will complete a circuit through the left hand half of balanced solenoid 208,* as follows: From transformer secondary |9| through wire |92, Wire |13, wire 23|', contacts 22| and 220 of switch S, wire 23|, left hand half of solenoid 208, wire 234, and wire '|93 back to the transformer. This will cause solenoid 208 to swing the movable contacts 204 and 205 of switch R into engagement with the fixed contacts 2|| and 2|0, respectively, and will complete the actuating circuit lfor motor |96, as already described. This motor will'now rotate the worm 200 and worm wheel 20|, causing a movement of shaft H2 and crank arm ||3 in such a direction as to-lower the left hand end of lever 99 (Fig. 2) and partially close the valves 38 and 39, or limit the possible 1 229 which engages in slot 226 to swing the switch 'assembly S to the right until contact 22| is disengaged `from contact 220, lthus breaking the circuit through balanced solenoid or relay 208,

which is so constructed that'it will automatically circuitthus stopping the motor |96, :The arcuate extent of this swinging movement of switch return to neutral position and break the motor bracket 223, and consequently the time during 1 which motor |96 will' operate and Ithe distance through which the valves will be moved, will depend upon the arcuate distance through which contact member -220 has been moved by-means,

of the balanced solenoid |16, which in' turn is proportionate ,tovthe variation in temperature from the desired standard. It will thus be seen that the valves 38 andf39 will be closed an amount proportionate to the temperature varia,-

tions above the described standard effectiva.

temperature. In an exactly analogous manner, in l case the' effective temperature falls below the desired standard, contact |26 will be moved to the left, thus causing movabley switch member,

2|9 to close the circuit through contacts 220 Y By adjusting th pin 22s radially of disc 221,

the distance through which the-valves will be moved in proportion to any temperature varia tion can be adjusted. In case pin 229 is positioned substantially coaxial with disc 221, it will be noted that no swinging movement of switch assembly S will resultfrom the rotation of the eccentric disc. Inlsuch case, the motor |95 or |96as the case may be, would continue to rotate indeixiitely, or until the movable contact 220 is returned to its central position. For this reason the limit switches 202 and 203 are provided. In the example here shown, each of these limit switches comprises a fixed contact 235 and a movable contact 236 carried by one arm 231 of a switch lever pivted centrally at 4238.` A pair of valves, one of these 'arms' 239 will engage inner arm 246 of the switch lever, thus moving contact 236 away from ilxed contact 235 and breaking the circuit. When the pressure is removed fromswitch arm 248, the contact 236- swings back into engagement with xed contact The above discussion has assumed `that switch O was thrown to the right so that the system was under the control-of the day thermostat L. If Y l illuminating lights |86 andl |81 (already deswtch O is thrown to the left,l the' system will be controlled in exactly the same mannerby thenight thermostat L' which is, however, ad-

justed to maintain a lower temperatiire.` The automatic switch O is under .the control of the j time-controlled mechanism indicated generally at-T. The detailed construction of 'this timecontrolled mechanism is not a part of this invention, the apparatus used being of the type in which the quick-acting switch 24| isoperated directly from the clock mechanism and is closed at a certain hour vto throw the thermostat L' into control, and is .opened inithe morning to again place thermostat L in' control. The switch 242is" automatically` closed at periodic intervals to energize the motor 243 to" rewind thel clock'.

When switch 24| is closed by the clook'mechanism, a circuitisycompletedbetween the two power-lines |88 and |89 as follows: Through wire 244, magnet coil |69 of switch O, wire 245 to the switch 24|-, and wire 246 to powerI line |89. The energization of magnet |69 throws switch O -tothe left so as to place the night thermostat .in co'ntrol.

If manually operated switch P is thrown from its upper to its lower position, the automatic control by means of the thermostats is thrown out of service, and the heating system may now becontrolled manually Jby means of the appara tus indicated generally at V. This comprises-a xed resistance 241 which corresponds to the re sistance |2| in the.therm`ostat L. Amovable' contact 248. engages thisresistance intermediate its ends, the contact member being carried by a pointer 249 pivotally mounted at its lower endA 248 is connected by wire 253 with the lower central contact of switch P, and the two lower out- ,side contacts of this. switch are vconnected by wires 254 andl 255 with the respective ends ofresistance li241. By manually moving the contact 248 by turning knob 25|, the relative proportions of the two sectionsv into which resistance 241 is divided will control the heating system in exactly the same-manner as described in connection with the automatic operation of the thermostats L and L'. The wires 253, 254 and 25s' simply take the place, in the control circuit rst de i jscribed, of the wires |29, |30 and |3|. v

The temperature. indicator W on thefpanel' board comprises a balanced solenoid 256 which Ais connected in parallel, through wiresA 251, 258

and 259 with the'balanced solenoid- |16 which operates the proportioning switch S. Thecore the steam supplyA is being increased or decreased.

of this` solenoid 256 operates, through plunger 26|).v a pOinter 26|, which indicates the room temperature on a dial or scale 262.

Apair of signal lights 263 and 264 on the control panel M indicate at any'moment whether One side of each of'these lights is connected aiiaw'f` the through wire zes with the power line las. The

other side of light 263 is connected through wire 26s with the iixed Contact zit of switch R, and the other light 264 is connected through wire 261 with the fixed contact 2|,| of switch R. The' `movable contact 204 of switch R completes the circuit through one'signal light or. the other, de-` pending on -whether it is'in engagement with fixed contact2`| For fixed contact 2 I6.

It will be noted thatthe constantly burning scribed) are -not indicated in Fig. 9, since indiv rect lighting o f the panel board-is used. However, theselights,fif desired could be placed on .the face of the board for direct lighting.

The inotor 8 which drives the `pump 1 is directly controlledthrough the mechanism indiwhich is a. switch AX by means of which .the

Iautomat-.ic control ofthe pump can be thrown out of service and a manual control substituted; a switchY which, determines 'whether or notA the time-'controlled mechanism shall effect the anisms mounted on the panel board M,vamong operation'of the fpump, and'a quick-acting relay Z. The pump motor and the controllingdevices therefor do'not receive their power from the same power source |11 from-which the mechanisms previously described are'energized, 1

lines 268, 269 and 210 (see lower left hand corner of Fig. 1o). 'At 21| are indicated' the terminals of a three-phase alternating current motor 8 or the starter. therefor. At 212 is indicated a' three-pole switch which is normally open to stop the vmotor, but which may be closed .to

start the motor by means of the electro-magnet. 213. At 214 is indicated a thermal overload-re-v lay which ishormaliy closed and is 'in circuit with the actuating magnet 213. Incase ot an execssive current or overload, this switch 214-'will open in. well known manner so `as to break the `motor circuit. Whenever switch 3| is closed (this switch being controlled by a float in theaccumulator tank G, as already described) a circuit willbe completed'through one phase of 'the alternating currenit circuit as follows:

From wire 268 throughv'wire 215, switch 3|, wire 216, magnet 213, and thermal switch 214 to the power line 269. In this 'manner the motor willbe started to operate the exhausting mechanism whenever a. sufficient quantity of conden'sate has' collected in the accumulator tank G, and the motor will be stopped whenever this condensate has' been withdrawn into the separating tank 6 since the switch 3| will then open and de-ener- 'gize magnet 213. Thepswitch 3| is in control of completed, extend .respectively to the terminals 219 and 2860i an automatic switch 28| positioned on thepanelboard. 'I'his switch 28| is normally closed so asto extend the circuit to terminals 282 andn 283 from which wires 284 and 285 extend, `respectively, tothe two xed contacts 286 and 281 of the relay Z. fIhe movable contact plate 28,8 of this relay vmay be moved Llp t0 close the circuit through contacts 286 and 281 by means of the magnet device, indicated at 289. Whenever the relay Z is closed in this manner, the circuit will be.comp`leted through wires 211 and 218 so' as to energize magnet 213 and close switch 212, thus starting the motor 8.

The energizing circuit for magnet 289 which closes the relay Z includes the switch 2| of differential-pressure controller J, one side of which is connected through wire 299| with the central power lead 269, and the other side of which is connected through .wire 29| with terminal 292 of the relay device. A wire 293 extends from this terminal to the magnet 289... It will thus be apparent that whenever the necessary pressure differential has been established, and switch 2| has consquently'been opened, the magnet 289 will be de-energized, and consequently the pump motor will cease to operate.

When the automatic control ofthe pump mo. tor is in effect, the switch X will be closed, at which time the actuating circuit for magnet 289 will extend from this magnet through wire 294, terminal 295, wire 296, through' one arm of switch X, wire 291 to the movable contact 295 of switch R, -'xed contact 299, wire 298, central arm of switch X, wire 299, terminal 399, and wire 39| to fixed contact 281 of relayZ, thenceV back n current circuit whenever differential-controller switch 2| is closed and the switch R ismoved to theright, which latter will occur when the valve is adjusted for .increasing the steam supply. The energization of magnet 289 will close the .movable contact 288 of relay Z against the fixed contacts 2st and 281 and result in the closing and thence as in the original circuit. Thiscircuit will remain complete and the pump will continue1in operation until the pressure diierential vhas been established and switch 2| is opened, v or until the desired effectivev temperature has beenl established,v at which time the energizing circuit for 'magnet '289 is short-circuited, by

.. means of the temperature-indicator W. The 1 ypointer 26| of this temperature indicator carries a contact 394 which is adapted to engage a contact 395 carried by a, lever.396 which is move'd about its fulcrum 391 by a plunger 398 extending from the humidity-,compensator 399.

The object of this humidity compensator 399 Y is to so Vary the position of movable contact 395 that the engagements between contacts l394 and 395 will occur at a. higher temperaturefor decreasing humidities and at. a lower temperature for increasing humidities. this humidity vcompensator 399 may be similar to that already described-in connection with the thermostat L, or any other suitableform.

Whenthe effective temperature has been raised to such a point that contact-394 engages contact 395, a shunt circuit about the magnet 289 is established as follows: From terminal 292 through wire 3|9, resistance 3U, wire '3|2.' ter- The i construction of.

minal 3|3, wire 3|4; switch X, wire 3|5, contacts 395 and,394 of temperature indicator W, wire 3|6, switch X, wirel 296 and thence as in they previously described circuit. The v completion of this circuit will short circuit magnet 289 and cause the relay Z to open, whereupon the pump motor will stop.

It is sometimes desirable in the interest of economy, or for some other reason', to have4 the 1differential-pressure control and thermostatic control of the pump continue only in the day time, but be thrown out of service at night, at which time the pump is only started by means of switch -3| when sunicient condensate has accumulated in the tank G. In order. to bring about this operation, the switch X remains closed, but switch Y is thrown to its vlower position so that, as indicated on the panel board M, the pump-time control is in force. The normally closed switch 28| is automatically opened whenever the magnet 3|1 is energized. This magnet is energized whenever the time-control mechanism T has thrown the night thermostat L' into control, the circuit being` as follows:-

From wire 244 through wire 3|8, magnet 3|1, wire 3|9, one arm of switch Y, and wire 329 to wire 245. This circuit is in parallell with the energizing circuit for magnet |69 of switch. O,

so that it will be seen that wheneverthe switch O is thrown to place night thermostat L in operation, the magnet 3I1 will be simultaneously energized to open the switch 28|, thus breaking the automatic 'control circuits for the pump. It will be noted that .when switchY is in itsupp'er position (so as to throw out the time-control of the pump) a shunt circuit fis formed around the automatic switch.. 28| through wires' 32|, 3,22, switch Y'and wires 323'and 324. though switch'28l 'is opened` as the result of the time mechanism T, throwing the thermostat L' into service, the pump control circuits will stilll remain complete.

If switch X'is openedrv so as to\throw the automatic pump control out of operation, the pump motor can still be stopped andstarted manually by means of the push-button switches 324 and 325, that is, providing the pressure diier ential has not been established and switch 2| at the differential controller is closed. The switch f.

324 completes a shunt circuit between wires 296 and 299. so as to temporarily establish the/same K Thus, even circuit' that is automatically closed by the.

lpointer 26| .of temperature indicator W.

In addition to this differential pressure control and in direct cooperation therewith is the automatic temperature and humidity control mechtemperature` is maintained. in the building being heated. The greater part of the manually operable devices for regulating the heating system, and the apparatus for indicating the condition of the heating system, are centralized on the control "of the pump. Switch Y is'thrown-up panel board M 'which may be positioned in any convenient location. In case a fully 'automatic control of the heating system is to be 'maintained throughout the' day and night, the several switches are positioned asshown in Fig. 9. Switch PJ is thrown up so as to-place the automatic temperature control system in service.v

Switch X is also thrown up to insure automatic so as to put the tune-control of the punp out of 7service, that is the pump will be automatically controlled by the dierential controller and `(or L') exceeds the predetermined standard eiective temperature for which the thermostat is adjusted, or the average effective temperature throughout the building exceeds the standard temperature in case a plurality of thermostatsl are used, this thermostatic mechanism will cause the electrically operated mechanism K to partially close the valve C and cut down the ilow of steam to the radiators." Thel valveC will still be under the control of the differential-pressure operating mechanism, but the maximum opening of the valve C will be limited by the position of ontrol lever 99, which is determined by the action of the thermostatic mechanism. In

case the effective temperature falls' below the desired standard, -lever 99 will be automatically adjusted so asto permit a wider opening of the control valve C, this opening ofthe vvalve will be effected by the diierential-pressure control mechanism at such a rate as to maintain the proper eiiicient supply of steam to the radiators. If the steam supply is being increased at any time, this will be indicated by the signal light 263 on the panel board, and if the steam supply is being decreased, the light 264 'will be lighted. The room temperature existing at the thermostat or thermostats is indicated by the mechanism W on the panel board. Atrthe same time, the pump motor is being automatically controlled so as to maintain the necessary pressuredifferential between the supply and discharge sides of the radiators. l pressure differential hasv been established, the

Y pump will be stopped bythe opening of switch YAt such times, the suppl'y ,of steafm is beingcut down and thefunctioning of the pump is temporarily unnecessary. However, as soon asthe thermostats indicate the need for an increase of the steam supply, the switch R will close the` Whenever this d ontrol circuit at 205, 209 so that the pump can again operata-in case the necessary pressureV Adiierential is no llonger est'iablished 'and .the anism 'whereby a substantially, constant eilec'tive switch 2l is closed. In any event,- ,the pump can bestarted in op'eration at any-.time by the closing of switch-3| in order to remove an excess of condensate from the accumulator tank G.

In case it is deswired -to discontinue the differ--v ential-'pressure control ofthe pump at night, the-'switch Y is thrown to its lower position,

whereupon the pump will -be automatically con trolled as above described during the daytime, but at night will only b e operated when neces- 'sary to remove .condensate from the accumuiator tank. By throwing 'switcii x to its lower` position, the automatic operation of the pump lby means of the diil'erential-controller and the thermostatic mechanism can be entirely discontinued without affecting the automatic operation of the remainder ofv the mechanism; At such times, or in fact at any time, the pump can be automatically started and stopped at will, by means of the pushl buttons 324 and 325.

`In case it is desired to throw the thermostatic control mechanism out oi?, service and.- control the system manually, the switch P is thrown to its lower position. The operator can lthen control the system to increase or decrease the possible opening of valve C and thus regulate the steam supply by turning the knob 25| onv the vpanel board, the positioning of the valve being indicated on the scale 252. -w

The entire electrical temperature control system, as centralized on the panel board, can be Y Opening 'the main thrown out of service switch- `IBI). However, even under these conditions the heating system will still be operable,

although in a less effective manner. It will Be remembered that the pump motor is supplied from a separate alternating current circuit, and the pump will still be automatically thrown -into operation whenever a sufficient quantity of conl densate has accumulatedl in tank G 'so as to remove this condensatend at the same time,

time to maintain the'pressure differential, the

valve C will remain open and steam from generator A can ow continuously into the radiators. `While the mechanism hereinabove disclosed by way of example is especially designed for use with aheating system utilizing steam at sub-atmospheric pressures, it will.be apparent that the invention, in itsbroader aspects, relates to va system of vmaintaining effective' temperatures in accordance with changes both in l the temperature and -the humidity of the air, e

and can be applied to other types of heating systems, such as those utilizing steam at superatmospheric pressures,` or hot water, as a heating medium. 'i The invention disclosesa system of` air-conditioning wherein, instead of attempting to regulate the actual humidity of the air-,the

dry-bulb temperature is varied inversely with changes in the humidity. From this broad viewpoint, the actual heating medium used is o! secondary importance.

The improved Vapparatus combination herein disclosed for carrying loutthis l'method is disclosed and claimed in the copending divisional application, Serial No. 713,862, filed l'March 3,

v1 934, exceptlor the specific thermostatic de.

vice for controlling, the heating system, which latter is disclosed and claimed in a second divi- 75 sion of .this present application, Serial No. 752,623, led November 12, 1934.

We claim:

1. The method of heating by steam which' -space when this differential falls below a predetermined standard and decreasingthe rate of steam supply when the differential rises above this standard, and automatically limiting the maximum rate of steam flow into the space in accordance with both temperature and humidity changes in a space that is heated by heat given off from the condensing space, this maximum rate being increased when the temperature in the space to be heated falls or when the humidity decreases, and decreased when the tem perature rises or the humidity increases.

2. The method of heating by steam which consists in introducing steam into a condensing space having separate supply and discharge.

ducts, effecting the withdrawal from said space of non-condensable gases and condensate while retaining the steam therein,` maintaining a pressure in the discharge duct lower than the pressure in the supply duct by a substantially constant diierence suicient to keep up circulation, automatically increasing the rate of steam supply through the supply duct to ythe condensing space when this differential falls below a predetermined standard and decreasing the rate of steam supply when the dierential risesvabove this standard, and automatically limiting the maximum rate `of steam ow into the space in accordance with both rtemperature and humidity changes in a space that is heated-by heat given oi from the condensing space, so as to maintain `a relatively higher temperature in the space to be heated as the humidity in this space decreases, and a relatively lower temperature when the humidity increases.

CLAYTON A. DUNHAM. DAVID N. CROSTHWAIT, JR. 

